The present invention relates to an adjustable chair in general, and more particularly to a chair which can be converted into a cot by changing the inclination of the backrest relative to the seat.
There are already known various constructions of adjustable chairs of the type here under consideration. In one type of the adjustable chair constructions, a seat is arranged between a pair of lateral portions of a frame, and a backrest is connected to the seat for pivoting relative thereto between an erect position and a fully reclined position. A leg rest is connected to the seat for pivoting between a retracted position and an extended position, and a connecting arrangement connects the backrest with the leg rest so that they simultaneously move between their respective positions. Thus, when the backrest is in its erect position, the leg rest is in its retracted position so that the person using the adjustable chair can use it as a chair, whereas the leg rest assumes its extended position when the backrest is in its fully reclined position so that the user of the adjustable chair can assume a prostrate position thereon. A pair of armrests is pivoted on the backrest, and the respective armrest is provided with a plurality of teeth arranged in a row and extending toward the upper portion of the associated lateral portion of the frame on which there is provided an arresting tooth which engages the teeth of the row so as to arrest the backrest in its respective angular position relative to the frame. The pivoting movement of the armrest relative to the backrest results either in disengagement or in engagement of the detent tooth with the teeth of the row so as to enable the user of the adjustable chair to change the angular position of the backrest relative to the frame.
In the adjustable chairs of the above-mentioned type, the user of the adjustable chair has to subject the backrest to an adjusting force when it is desired to change the angular position of the backrest, such force being attributable to the weight of the user of the adjustable chair. It will be appreciated that the part of the weight of the user which is applied to the backrest will increase with the increasing angle which the backrest assumes with respect to the vertical. This, of course, is disadvantageous inasmuch as, on the one hand, the force applied to the backrest increasingly exceeds the force which is necessary for adjusting the angular position of the backrest and, on the other hand and as a result of the former, the speed with which the backrest approaches its fully reclined position increases with decreasing angle between the instantaneous position and the fully reclined position. One disadvantage of this increasing speed of movement of the backrest is that it is increasingly difficult to arrest the backrest in a selected position as the frame approaches the fully reclined position thereof. Also, the interengagement of the arresting teeth becomes increasingly hard because of the increasing inertial and other forces which are to be overcome in order to stop the backrest in its partially reclined position. Thus, not only are the interengaging teeth subject to a high degree of wear, but also some discomfort is felt by the user of the adjustable chair as a result of the deceleration of the backrest to a sudden stop. This is particularly true when the user holds the armrests provided with the arresting teeth and lifts the armrests in their disengaging positions so that the backrest performs its movement from the erect position or from one of the intermediate positions all the way to the fully reclined position. In this situation, the final abutment provided at the armrest and cooperating with the tooth provided on the lateral portion of the frame abuts against such detent tooth with full force, and the pivoting of the backrest is suddenly stopped from a high speed with a considerable impact. Such a quick pivoting of the backrest and such a sudden stop thereof may scare the user of the adjustable chair, particularly when the user is unfamiliar with the adjustable chair and with the operation thereof. This is particularly unacceptable in view of the fact that, more likely than not, the adjustable chair will be used by an older person. Also, the increased wear of the cooperating arresting teeth resulting from the substantial impacts which occur during the interengagement of the teeth to arrest the backrest in the desired position, particularly when such desired position is close to the fully reclined position, results in reduced useful life of the adjustable chair, which is also undesirable.